It has been known, when a plant (controlled object) has nonlinear characteristics, to model the plant by linear elements and nonlinear elements, to correct inputs determined by a linear controller through a nonlinear compensator so as to determine the final control input, as taught, for example, by Patent Reference 1 mentioned below. By the use of such a nonlinear compensator, the technique described in Patent Reference 1 has an advantage that can control a plant having nonlinear characteristics with high accuracy.
Patent Reference 1: Japanese Laid-Open Patent Application Hei 9 (1997)-297240.